Fluorescence microscopy is an indispensable tool for the quantitative analysis of the molecular pathways involved in disease. Importantly, heterotypic cell-cell and cell-matrix interactions within the 3D tumor microenvironment critically influences signaling pathways and hence the tumorigenicity of cancer cells. Therefore, it is important to study cancer cells in physiologically relevant conditions, which can be realized by using model organisms or organotypic organoid cultures. However, technological limitations prevent the observation of cancer cell dissemination and survival throughout an entire organism with sufficient spatiotemporal resolution to evaluate the molecular pathways and oncogenic states of individual cancer cells. Here, we propose to break through this barrier by developing a new optical microscope that is capable of longitudinally imaging an entire organism, but can also provide local high-resolution imaging. Furthermore, it can also perform 3D photo-manipulation, which allows temporally and spatially confined perturbation of intracellular signaling, modification of the microenvironment, and tagging cells of interest. The most important properties of the new microscope are i) multi-scale imaging at cellular and subcellular level, ii) minimal light exposure to allow long observation spans while limiting photo-toxicity, iii) increased optical penetration depth via adaptive optics, iv) isotropic spatial resolution in the high-resolution mode and v) 3D photo-manipulation using two-photon absorption. Optical modules will be developed that enable tunable light-sheet control, wavefront correction for adaptive optics, 3D scanning for photo- manipulation and variable magnification of the detection path. Thus, for the first time, this instrument will allow us to image cancer cell dissemination on an organism scale over extended time periods and also monitor and manipulate cell signaling states and morphodynamics with sub-micron, isotropic resolution in metastatic niches.